Control system for brakes for the wheels of aircraft



CONTROL SYSTEM FOR BRAKES FOR THE WHEELS OF AIRCRAFT I F. J. TARRls Filed Deo. 26, 1933 CII Patented Dec. 17, 1935 UNITED STATES CONTROL SYSTEM FOR BRAKES FOR THE WHEELS F AIRCRAFT Frederick John Tnis, London, Englandkassignor to The India Rubber,

Gutta Percha and Telegraph Works Company Limited, London, England, a British company Application December 26, 1933, Serial No. 703,968

In Great Britain January 4, 1933 'nclaims (cl. 244-29) This invention comprises improvements in or relating to control mechanisms for the operation of brakes for the wheels vof aircraft 'and in particular relates to that type of control mechanism in which the brakes may be operated from either of two control positions inthe aircraft.

The invention is very advantageous in aircraft irrespective of their use and particularly advantageous in aircraft used for training purposes during which use one (or the first) control position is that occupiedvby the instructor andthe second control position is that occupied by the pupil. Throughout the present specification and claims therefor thetwo control positions will be designated as the instructors position? and the pupils position respec-` tively. `Similarly actuators, for effecting operation of the brakes, located at these` respective' positions will be referredr to as the instructors actuator (or. actuators) and the ,pupils actuator (or actuators) It is to be understood however that these terms are used only for the purpose, of differentiating vtwo. control positions in an aircraft having means `for dual control and are not intended to limit the scope of the invention Kin any way. u

According'to the present invention a control mechanism for the operationv of aircraft Wheel brakes', comprising actuators situated in the aircraft at an instructors position and also at a pupils position from either of which positions the Abrakes may be operated by said actuators, is provided with-'means operable from the instructorsl position to render the vactuator (or actuators) at the pupils position inoperative upon the brake or brakes and at the same time leave the instructors actuator (or actuators) capable of operation upon the brake or brakes.

Preferably lin such a Acontrol mechanism an operative connection between an actuator at the pupils position and a wheel brake or brakes is, at an intermediate point in said operative connection, coupled to an actuator at the instructors position in such a mannenthatV operation of the last-mentioned actuator renders vthe aforesaid pupils actuator inoperative.

Fluid conduits are arranged to provideI communication between the instructors "and the and also to divert awayfrom the latter'pressure fluid subject to the control of the pupils actuator (or actuators) without interruption of communication between the instructors actuator Y' (or actuators) and the brake mechanism.

Preferably, in the form of construction last referred to, each control position is provided with an actuator 'or actuators whereof each comprises a pressure producing device and whereof the instructors actuator (or each of them) is in direct communication with the brake mechanism and the pupils actuator (or each of them) is in communication with the brake mechanism through the intermediary of a valve combined with operating means therefor operatively connected to the corresponding instructors. actuator so as to open the valve only when the said instructors actuator is in or is approximately in an inoperative position, and there is furtherprovided a reservoir or expansion chamber and meansoperable at will from the instructors position for diverting to said reservoir or expansion chamber pressure liquid from the pupils actuator (or each of them) with which the said means is in direct communication.

In a control mechanism according to the in# vention for aircraft vwheel brakes operated by fluid pressure the conduit providing communication between the pupils actuator and the brake mechanism preferably comprises,las part of it,l the Whole or a portion of the conduit providing communication between the instructors actua-v tor and the brake mechanism', a valve being provided to control the conduit leading from the pupils actuator to the junction with the conduit leading from the vinstructor-s actuator. `35 Again in a control mechanism as previously described for brakes operated by liquid under pressure there is preferably provided a con-` duit forming a by-pass to the reservoir or expansion'chamber and joining the connectionbe- 40 tween the pupils actuator (or each' of them) and the instructors actuator, a valve in said conduit and operating means for said valve operable at will from the. instructors position. Preferably also a conduit connects the pupils 45 actuator (or each of them) with the reservoir or expansion chamber and is' provided with a` valve which is such as to allow liquid to now from the reservoir into thev actuator only when the latter is in or approximately in a normal inoperative position of rest.

In some cases all the wheel brakes of the air' craft may be controlled `by a single ,control mechanism according to this invention-,but preferably the brake or brakes of the wheel or wheels on`oney side of the aircraft are controlled by one mechanism according to this invention and the brake or brakes on the wheel or wheels on the other side of the aircraft are controlled by another similar mechanism. According to the latter arrangement the brakes may be used for the purpose of steering the aircraft when on the ground. With such a construction with the brakes operated by liquid under pressure, the two control mechanisms are provided with a single reservoir or expansion chamber to receive the pressure liquid directed from the pupils actuators.

The accompanying drawing shows the arrangement of parts in one constructional form of the invention, in which form separate control mechanisms are respectively provided for liquid operated brakes on opposite sides of the fore and aft centre line of the aircraft, the two control mechanisms having a` common reservoir.

Referring to the drawing, A and B indicate generally the two actuators of the first or inl structor's control position in the aircraft and X and Y similarly indicate the two ractuators of the second or pupils control position. The actuators A and X belong to one of the two separate control systems and the actuators B and Y to the other.

Each actuator comprises a cylinder l having' a piston l movable therein upon the actuation of a pivoted, pedal 5, the said piston being connectedinaknownmannertothewallofthe cylinder 3 by a `flexible folding diaphragm 6. Movement of the piston l by the pedal S is effected through a cam slot 1 in the pedal which engages the end of a gudgeon pin 8 extending -from the piston through a slot in the wall of n the cylinder 3. These slots are shown in dotted lines in the actuators B- and Y in which they are located behind the pedals 5. The piston 4 is urged by springs Il to the position in which the pressure chamber l enclosed by the diaphragm I is of maximum capacity. The pressure chamber 9 of. each of the actuators A and B communicates freely with a conduit III leading to the braking mechanism and also communicates with a conduit kII through a valve I2 which is arranged substantially as described in U. S. Patent No. 1,887,880 and which is only open to permit the flow of fluid from the chamber 9 to the said conduitii when the piston 4 is in or is approximately in a position which provides the maximum capacity o f the chamber 9, or in other words, when the lever i is in or approximately in its normal position of rest. The said valve is such, however, as to permit uid under substantial pressure to flowin the reverse direction, i. e'. from the said conduit II into the chamber I.

This operation of the valve I2 is effected by means of valve-spring |26 acting .on the head of the valve and tending to eifect its closure, and by means of the connecticn between thel valve-stem III and the pistoni which has a slot I!! to accommodate thevalve-stem Ill. The slot I2! is formed to co-operate at one end with the end of the valve-stem III when the piston I is at, or approximately at, that position affording a maximum volume of the chamber l, and this co-operationl is such as to move the valve oif its seat against the action of the valve-spr1n8 Ill. A

The 'conduit Il connected to the actuator A communicates with the brake or brakes on one side of the fore and vaft centre line of the aircraft and that of the actuator B with the brake or brakes on the other side of the aforesaid centre line.

The pressure chamber 8 of each of the actuators X and Y communicates freely with a conduit III) and also communicates with a conduit III through a valve I2 similar in construction to the valve I2 provided in each of the actuators A and B. 10

Conduits I I0 connected to the actuators X and Y respectively communicate through a three-way junction I3 with the conduits II connected to the actuators A and B. The other conduit II2 from each junction I3 communicates through 15 a valve indicated generally at C with a reservoir or expansion chamber indicated generally at D. Each conduit III of the actuators X and Y communicates directly with the reservoir or expansion chamber D. 2'0

The valve C comprises a diaphragm I6 which can-be thrust downwards by means of a cam capable of holding it in this position and lprovided with an operating lever I1. The lever i1 is operable from a position in the vicinity of the 25 instructors position. In the position described the diaphragm I6 shuts oif communication between the cavities I8, which communicate with the conduits II2 leading from the junctions I3, and the chamber I9 which communicates by'30 means of a conduit I4 with the reservoir D.

'I'he cam I6I acts upon the`diaphragm I6 through a leaf spring |62 having bosses |63 and I secured thereto and contacting with the diaphragm. This leaf spring |62 is normally 35 bowed away from the diaphragm I6 so that the lever I1 acts against said spring in thrusting the diaphragm I6 downwards to shut off communication between the cavities I8 and the chamber i9.

The reservoir D has a main chamber' 20 and a sub-chamber 2| communicating with each other through'the aperture 22. The conduits Hi from the actuators X and Y and the conduit I4 all communicate with the sub-chamber 5 2|. Located below the aperture 22 is a loose v alve member 23, which, when the reservoir is turned upside down, falls into a position which prevents fluid flowing from the subchamber 2l to the main chamber 20. On the 50 top of the reservoir an airvent is provided which is also closed when the reservoir is turned upside down by the ball valve 2l.y

In operation the pipe ,systems and cylinders of the actuators and braking mechanisms are filled with a suitable pressure liquid and it will be seen that normally the brake or brakes may be operated from either control position or by the simultaneous operation of the actuators of cath control positions. By means-of this simu.- taneous operation an instructor in the first con-y trol position can augment the pressure applied to either brakey by a pupil in the second control position. Wherethe occupants of both control positions have operated the actuators for cnc 55 or both brakes the occupant of the pupils csntrol position cannot reduce the braking pressure applied until the occupant' of the instructors position has ceased to operateI his actuator or actuators for operating the brakes. Should the pupil operate either or both actuators X and Y in such a manner as to put on the brake or brakes excessively or should the instructor for some other reason desire to release the pupils operation of the brake or brakes, he can do so by operating the lever I1 to open the valve 'C and by-pass the pressure liquid from the actuators X'and Y into the reservoir D where the liquid will remain until the pistons of the actuators X and Y. are returned to the positions at which the chambers 9 of said actuators have their maximum capacity. The reservoir D is positioned in the aircraft soyas to be above the actuators A, B, X and Y and consequently 'when' the pistons of the actuators 4X and Y reach the vposition which has just been described the pressure liquid will flow back under gravity by way `of conduits lll to the chambers 9 of the said actuators. i

Since the valves I2 of the actuators A and B close the communication between the chambers 9 of these actuators and the conduits Il leading vfrom them as soon vas the actuators are operated to apply pressure to thebrakes, the opening of the valve C does not prevent the continued operation of the brake or brakes by theI withpressure liquid. The valve 23 prevents` fluid owing from the pipe systems' into the reservoir when the aircraft is flying upside down and the ball valve likewise prevents the escape of Vfluid from the reservoir when the aircraft is in that position. c

Many modifications may be made in the form of the invention which has been described. The invention may beapplied to brakes operated by air or another gas. In the case of brakes operated by compressed air the conduit or conduits from the actuator or actuators at the pupils position are led to the brake or brakes through the actuator or actuators at the instructors position and a valve is provided by which, at the` will of the occupant of the instructors position, the air from the actuator or actuators at the pupils control position may be exhausted to atmosphere and the conduit from thesaid valve to the brake or brakesclosed so as to allow the continued operation of the brakes by the occupant of the instructors position.

I claim: f

1. For the operation of aircraft wheel brakes actuated by fluid pressure, a control mechanism lcomprising actuators, each of which is constition capable 4of operation upon the brakemechanism.

2. For the operation of aircraft wheel brakes actuated by pressure uid, a control mechanism comprising actuators, each of which is constitutedby a fluid-pressure control device, situated y in the aircraft at an instructors position and also at a pupils position from either of which positions the brakes may be operated by said actuators, means to provide .a fluid connection between an instructors .actuator and the brake mechanism, and means to provide a fluid connection between a pupils actuator and a corresponding instructors actuator in such a manner that operation of the latter actuator renders the aforesaid pupils actuator incapable of releasing fluid pressure applied to the brake mechanism.

3. For the operation of aircraft wheel brakes actuatedby iluid pressure, a control mechanism comprising actuators situated in the aircraft at an instructors and also at a pupils position from either of which positions the brakes may be operated, fluid conduits providing communication between the instructors and the pupils actuators-and the brake mechanism, and means operable at will from the instructors position to prevent iiow of pressure fluid from the brake mechanism at least in a direction towards the pupils actuator, and means to divert'away from the latter pressure iiuid subject to the control of the pupils actuator, without interruption of communication between the corresponding `instructors actuator and the brake mechanism.

4., A control mechanism according to claim 3 wherein the conduit providing communication between a pupils actuator and the brake mechanism comprises, as part of it, at least a portion of the conduit providing communication between the corresponding instructors actuator and the brake mechanism, and wherein a valve is provided to control the remaining part of the conduit leading from the pupils actuator to the brake mechanism.

5. For the operation of aircraft wheel brakes actuated by liquid under pressure, a control mechanism comprising actuators, each of which comprises a' pressure producing device, situated in the aircraft at an instructors position and also at a. pupils position from either of which positions the brakes may be operated, fluid conduits affording communication between a pupils actuator and the brake mechanism and between the instructors actuator and the brake mechanism, a valve to prevent flow of fluid pressure from the mechanism to the pupils actuator, operating means for the valve operatively connected to the corresponding instructors aotu^tor so as to open the valve to allow pressure uid to flow from the brake mechanism to the pupils actuator only whenthe said instructors actuator approximates' to its inoperative position, a reservoir, and means operable at will from the Vicinity of the instructors position and in direct communication with the pupils actuator to divert pressure uid therefrom to the said reservoir.

6. VFor the operation of aircraft wheel brakes a control mechanism Aaccording to claim 5 wherein the conduit providing `communication between a pupils actuator and the brake mecha-l nism comprises, aspart of it, at least a portion of the conduit providing communication between the corresponding instructors actuator and the brake mechanism and wherein the junction between the two conduits is located in the structure of the instructors actuator'V and wherein a. valve is located in the said structure adapted to close, at the junction, the opening of the conduit leading from the pupils actuator, and an operative connection is provided between said valve and the said instructors actuator.

7. For the operation of aircraft wheel brakes actuated by liquid 'under pressure, a control mechanism comprising actuators, each of which comprises a pressure producing device, situated in the aircraft at an instructors position and at a pupils position from either of which positions the brakes may be actuated, a iirst conduitproviding direct communication between an instructors actuator andthe brake mechanism, a second conduit providing communication between a pupils actuator'and the corresponding instructor's actuator, a valve located within the structure of said instructors actuator to close the end opening of said second conduit, operating means for the` valve operatively connected with said instructors actuator so as to open the valve only when the instructors actuator approximates to itsinoperative condition, a by-pass conduit joining the aforesaid second conduit, a reservoir communicating with the by-pass conduit, and a valve in said by-pass conduit in combination with.

operating means therefor operable at will from the vicinity of the instructors position.

8. A control mechanism according to claim 'I having a conduit connecting a pupil's actuator with the reservoir anda valve located in said conduit in combination with operating means therefor such as to open the valve to allow liquid to flow from the reservoir into the actuator only when the latter approximates to a normal position oi' rest. v

9. A control mechanism according to claim 7 provided with an automatically operative valve which comes into operation only when the aircraft is inverted to shut oil! communication between the reservoir and the conduits passing to the actuators and brake mechanisms.

j 10. A control mechanism according to claim 7 wherein the reservoir is provided with an air vent passage at its upper end and an automatically operativevalve for closing said passage, which valve only comes into operation when the aircraft is inverted.

11. A control mechanism according to claim 7 having a pair of actuators at the' instructors positionand a pair of actuators at the pupils position, and having the actuators of each pair separately associated with and connected to thebrake mechanisms situated on opposite sides of the centre line of the aircraft so that the brakes may be used for the purpose of steering when the aircraft is on the ground, and having also the pair of pupils actuators directly connected in common to the reservoir communicating with the by-pass conduit.

FREDERICK 'JOHN TARRIS. 

